USB: Mass storage gadget: Handle eject request

This patch adds handling of the "Start/Stop Unit" SCSI request
to simulate media ejection.

Signed-off-by: Fabien Chouteau <fabien.chouteau@barco.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 45 insertions, 3 deletions

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index 9dbe86dec332..c904aa39ad84 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -163,6 +163,10 @@
  * ro setting are not allowed when the medium is loaded or if CD-ROM
  * emulation is being used.
  *
+ * When a LUN receive an "eject" SCSI request (Start/Stop Unit),
+ * if the LUN is removable, the backing file is released to simulate
+ * ejection.
+ *
  *
  * This function is heavily based on "File-backed Storage Gadget" by
  * Alan Stern which in turn is heavily based on "Gadget Zero" by David
@@ -1384,12 +1388,50 @@ static int do_mode_sense(struct fsg_common *common, struct fsg_buffhd *bh)
 
 static int do_start_stop(struct fsg_common *common)
 {
-        if (!common->curlun) {
+        struct fsg_lun  *curlun = common->curlun;
+        int             loej, start;
+
+        if (!curlun) {
                 return -EINVAL;
-        } else if (!common->curlun->removable) {
-                common->curlun->sense_data = SS_INVALID_COMMAND;
+        } else if (!curlun->removable) {
+                curlun->sense_data = SS_INVALID_COMMAND;
+                return -EINVAL;
+        }
+
+        loej = common->cmnd[4] & 0x02;
+        start = common->cmnd[4] & 0x01;
+
+        /* eject code from file_storage.c:do_start_stop() */
+
+        if ((common->cmnd[1] & ~0x01) != 0 ||     /* Mask away Immed */
+                (common->cmnd[4] & ~0x03) != 0) { /* Mask LoEj, Start */
+                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                 return -EINVAL;
         }
+
+        if (!start) {
+                /* Are we allowed to unload the media? */
+                if (curlun->prevent_medium_removal) {
+                        LDBG(curlun, "unload attempt prevented\n");
+                        curlun->sense_data = SS_MEDIUM_REMOVAL_PREVENTED;
+                        return -EINVAL;
+                }
+                if (loej) {     /* Simulate an unload/eject */
+                        up_read(&common->filesem);
+                        down_write(&common->filesem);
+                        fsg_lun_close(curlun);
+                        up_write(&common->filesem);
+                        down_read(&common->filesem);
+                }
+        } else {
+
+                /* Our emulation doesn't support mounting; the medium is
+                 * available for use as soon as it is loaded. */
+                if (!fsg_lun_is_open(curlun)) {
+                        curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
+                        return -EINVAL;
+                }
+        }
         return 0;
 }